Does detaching EC2 Volume save cost

Question

I just got hit with a large EC2 bill while I didn't have more than one machines running.

After investigating my bill in a bit more detailed I saw that we were paying $1100 per month for provisioned IOPS. This turned out to be caused by 10 volumes of 1000 IOPS each for servers which had long since been switched off.

My question is whether Detaching these volumes will stop me paying for them. Or do I need to delete these volumes fully.

I don't mind paying a small cost for keeping them around in case we might need them again, but paying $1100 per month just to keep them lying around is ridiculous.

Answer 1

From what I know (and what I can confirm from the EC2 Documentation), Amazon does not charge you for an instance which is stopped. But they do charge for EBS volumes.

Quoting from the documentation:

When you stop an instance, we shut it down. We don't charge hourly usage for a stopped instance, or data transfer fees, but we do charge for the storage for any Amazon EBS volumes.

Also quoting from here:

Provisioned IOPS is charged by the amount you provision in IOPS (input/output operations per second) X the percentage of days you provision for the month. For example, if you provision a volume with 1000 IOPS, and keep this volume for 15 days in a 30 day month, then in the Virginia Region, you would be charged $50 for the IOPS that you provision ($0.10 per provisioned IOPS-Month * 1000 IOPS Provisioned * 15 days/30).

Since you provision the input/output operations, you pay for them even if you don't actually use them. So as long as you have provisoned IOPS, even if the EC2 volume is stopped and even if the EBS volume is not attached to an EC2 instance, you will have to pay for it.

Sorry about the huge bill you got for a service you were not using :( Have you tried contacting Amazon about this issue? Maybe they will reduce the amount or scratch it off from the bill alltogether?